The recipe for attracting visitors to stories online is changing. Bloggers have traditionally turned to sarcasm and snark to draw attention. But the success of sites like BuzzFeed and Upworthy, whose philosophies embrace the viral nature of upbeat stories, hints that the Web craves positivity.

The reason: social media. Researchers are discovering that people want to create positive images of themselves online by sharing upbeat stories. And with more people turning to Facebook and Twitter to find out what’s happening in the world, news stories may need to cheer up in order to court an audience. If social is the future of media, then optimistic stories might be media’s future.

“When we started, the prevailing wisdom was that snark ruled the Internet,” says Eli Pariser, a co-founder of Upworthy. “And we just had a really different sense of what works.”

“You don’t want to be that guy at the party who’s crazy and angry and ranting in the corner — it’s the same for Twitter or Facebook,” he says. “Part of what we’re trying to do with Upworthy is give people the tools to express a conscientious, thoughtful and positive identity in social media.”

And the science appears to support Pariser’s philosophy. In a recent study from the Massachusetts Institute of Technology, researchers found that “up votes,” showing that a visitor liked a comment or story, begat more up votes on comments on the site, but “down votes” did not do the same. In fact, a single up vote increased the likelihood that someone else would like a comment by 32%, whereas a down vote had no effect. People don’t want to support the cranky commenter, the critic or the troll. Nor do they want to be that negative personality online.

In another study published in 2012, Jonah Berger, author of Contagious: Why Things Catch On and professor of marketing at the Wharton School of the University of Pennsylvania, monitored the most e-mailed stories produced by the New York Times for six months and found that positive stories were more likely to make the list than negative ones.

“What we share [or like] is almost like the car we drive or the clothes we wear,” he says. “It says something about us to other people. So people would much rather be seen as a Positive Polly than a Debbie Downer.”

It’s not always that simple: Berger says that though positive pieces drew more traffic than negative ones, within the categories of positive and negative stories, those articles that elicited more emotion always led to more shares.

“Take two negative emotions, for example: anger and sadness,” Berger says. “Both of those emotions would make the reader feel bad. But anger, a high arousal emotion, leads to more sharing, whereas sadness, a low arousal emotion, doesn’t. The same is true of the positive side: excitement and humor increase sharing, whereas contentment decreases sharing.”

“It’s not that people don’t share negative stories,” says Jack Shepherd, editorial director at BuzzFeed. “It just means that there’s a higher potential for positive stories to do well.”

Upworthy’s mission is to highlight serious issues but in a hopeful way, encouraging readers to donate money, join organizations and take action. The strategy seems to be working: barely two years after its launch date (in March 2012), the site now boasts 30 million unique visitors per month, according to Upworthy. The site’s average monthly unique visitors grew to 14 million people over its first six quarters — to put that in perspective, the Huffington Post had only about 2 million visitors in its first six quarters online.

But Upworthy measures the success of a story not just by hits. The creators of the site only consider a post a success if it’s also shared frequently on social media. “We are interested in content that people want to share partly for pragmatic reasons,” Pariser says. “If you don’t have a good theory about how to appear in Facebook and Twitter, then you may disappear.”

Nobody has mastered the ability to make a story go viral like BuzzFeed. The site, which began in 2006 as a lab to figure out what people share online, has used what it’s learned to draw 60 million monthly unique visitors, according to BuzzFeed. (Most of that traffic comes from social-networking sites, driving readers toward BuzzFeed’s mix of cute animal photos and hard news.) By comparison the New York Times website, one of the most popular newspaper sites on the Web, courts only 29 million unique visitors each month, according to the Times.

BuzzFeed editors have found that people do still read negative or critical stories, they just aren’t the posts they share with their friends. And those shareable posts are the ones that newsrooms increasingly prize.

“Anecdotally, I can tell you people are just as likely to click on negative stories as they are to click on positive ones,” says Shepherd. “But they’re more likely to share positive stories. What you’re interested in is different from what you want your friends to see what you’re interested in.”

So as newsrooms re-evaluate how they can draw readers and elicit more shares on Twitter and Facebook, they may look to BuzzFeed’s and Upworthy’s happiness model for direction.

“I think that the Web is only becoming more social,” Shepherd says. “We’re at a point where readers are your publishers. If news sites aren’t thinking about what it would mean for someone to share a story on social media, that could be detrimental.”